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AR# 66431

High Speed SelectIO Wizard - DELAY_TYPE (FIXED|VARIABLE|VAR_LOAD) is not correctly set within the synthesized netlist


Version Found: 2015.3

The DELAY_TYPE (FIXED|VARIABLE|VAR_LOAD) is not correctly set within the synthesized netlist. This will affect the RX_BITSLICE, TX_BITSLICE, and RXTX_BITSLICE.

Note: this Answer Record should not be viewed in isolation.

For all other known issues and to see what version of Vivado / High Speed SelectIO Wizard these issues have been resolved in, please refer to (Xilinx Answer 64216)


The DELAY_TYPE value can be manually overridden by using constraints with the synthesized netlist.

Alternatively the user can edit the HDL file in the following location, following the flow described in (Xilinx Answer 57546):

The following 3 files need to be edited and can be found in the following directory:



       localparam [51*2+1:0] C_TX_DELAY_TYPE  =  {

.DELAY_TYPE((C_TX_DELAY_TYPE[(1+bs*2):bs*2] ==2'b00) ? "FIXED" : (C_TX_DELAY_TYPE[(1+bs*2):bs*2] == 2'b01) ? "VARIABLE" : "VAR_LOAD"),



.DELAY_TYPE((C_RX_DELAY_TYPE[(1+bs*2):bs*2] ==2'b00) ? "FIXED" : (C_RX_DELAY_TYPE[(1+bs*2):bs*2] == 2'b01) ? "VARIABLE" : "VAR_LOAD"),


   localparam [51*2+1:0] C_RX_DELAY_TYPE   =  {

   localparam [51*2+1:0] C_TX_DELAY_TYPE  =  {

.RX_DELAY_TYPE((C_RX_DELAY_TYPE[(1+bs*2):bs*2] ==2'b00) ? "FIXED" : (C_RX_DELAY_TYPE[(1+bs*2):bs*2] == 2'b01) ? "VARIABLE" : "VAR_LOAD"),

.TX_DELAY_TYPE((C_TX_DELAY_TYPE[(1+bs*2):bs*2] ==2'b00) ? "FIXED" : (C_TX_DELAY_TYPE[(1+bs*2):bs*2] == 2'b01) ? "VARIABLE" : "VAR_LOAD"),

If necessary, the edited IP can be packaged up and re-used. For more information see (UG1118).

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
64216 High Speed SelectIO Wizard - Known Issue list N/A N/A
AR# 66431
Date Created 01/19/2016
Last Updated 03/03/2016
Status Active
Type General Article
  • Kintex UltraScale
  • Virtex UltraScale